The present invention relates to a close-up focusing device for a photographic lens assembly, and, more particularly to a device for sliding certain lens components forward and backward along their optical axes to make the lens suitable for close-up focusing, so as to be adaptable particularly to office document copying use or photographing use and the like.
It has been known conventionally to provide a type of lens assembly known as a zoom lens, whose focal length can be varied continuously, and which permits a photographer to take close-up or long shots of a particular scene without having to actually move towards or away from the scene. Such zoom lens assemblies conventionally comprise a focusing lens, which is positioned foremost in the camera, a variator positioned behind the focusing lens, a compensator lens positioned behind the 1st magnifying lens, and a master lens which is positioned rearmost in the camera. Each of these various lenses generally comprises a group of lenses. Recently, in order to get close-up or macrophotographing in the zoom lens system above-referred to it has been proposed to employ a method of moving, in any one of the lens groups, certain of the lenses in such group relative to others in such group. However, this known close-up mechanism is designed such that it makes it possible to do the adjustment or manipulation for close-up photography only after setting every lens component of the lens assembly at predetermined positions and if the focal length for close-up is specified. Also, the conventional close-up mechanism for the zoom lens assembly is coupled to the zoom mechanism in a complex manner, so that it has a complex construction which makes it difficult to design as a power driving type system.